I find I my users are confused about what other people can see when they are using a category with broad access and a sub-category with more private access (which is the model I’m using a lot). They assume that because they can see the subcategory posts in the category then so can everyone else. And it is hard to educate them out of this.
Locks on the left, yes - both categories and subcategories. Categories limit access to a broad sector, subcategories to a sub-sector. So no good there.
Good education option, but I’m after a UX fix first if possible.